The present invention is concerned with a device which is designed for stacking batches of flat objects, especially batches of corrugated folding boxes or non-folded blanks of such boxes, which are arranged in successive layers on an appropriate loading plane or pallet.
In the present state of the art, there are devices called palletizers, which are capable of ensuring that batches of folded boxes or box blanks are stacked on a loading plane and especially on a pallet. The batches generally handled have a shape of a parallelepiped of relatively considerable dimensions and weights.
One of the known devices is described in my U.S. patent application Ser. No. 586,048, filed Mar. 5, 1984, which is based on French Application 83 04185, and whose disclosure is incorporated by reference thereto. As disclosed in this U.S. Patent Application, batches of boards, boxes or blanks are stacked on a loading plane in successive layers formed by the batches one after another. This operation is achieved beginning with a loading table or elevator with horizontally disposed rollers. The table or elevator is vertically movable between a fixed inlet level and variable levels corresponding to the height of the topmost surface of the stack of blanks on a pallet. Various batches are transferred from the appropriately placed inlet means at the fixed level onto the loading table. The table is then shifted vertically with the idea of having its position at a level corresponding to the plane on which the layer of batches is to be put on the stack of batches. The layer situated on the loading table is then lifted by a number of thin forks, which are arranged between the rollers of the table. The forks carrying the layer of boards, boxes or blanks are then moved perpendicularly to the direction of the arrival of the layers so that they will be situated above the loading plane or the previously placed layer. At this stage, a stop is then lowered in the rear area and the forks are withdrawn from underneath the layer, whereupon the layer will then be placed on the stack as the forks return to their initial position between the rollers of the loading table. The joint action of the stop and of the withdrawing of the forks will result in accurately aligning all superposed layers of the pile on a vertical line.
The number of layers wanted for a full pile having, thus, been attained, the pile will then be removed allowing for the possible build-up of a new or second pile.
Another device is disclosed in German Published Application OS 24 43 781 and this device also allows for a layer-wise superposition of batches of corrugated sheets. In this device, the previous batch of sheets are carried by a belt conveyor to the rollers of an intermediate station. The batches are then transferred into a batch collector before being moved into the piling station proper. The piling station has retractable components supporting the lateral parts of the batches carried into this station, as well as squaring devices for the batch layer shaped by the arrival of several successive batches. As soon as the number of batches which are supposed to be accumulated is obtained, retractable components are actuated, whereupon the batch layer is then put on a precedent layer already lying on a vertically shiftable pile delivery. As soon as the batch layer has been laid down, the pile delivery is actuated in such a way as to have it descend until the upper surface of the batch layer is again situated on the plane enabling the superposition of a new layer on the one already laid down. The stacking of the layers continues until the pile delivery will reach its lowermost position. At this stage, the arrival of the batches will be interrupted during a period required for the removal of the pile of batches and for the return of the pile delivery into a position it had in the beginning of the loading operation. Attention is to be drawn to the fact that the first device described above allows the stacking of layers made up by batches arranged side-by-side and crosswise with the rows thus formed being assembled behind one another on the loading plane in such a way that the layer will be stackable. The second device handles the stacking of batches arranged behind one another, therewith being coherent.
The devices described above usually operate satisfactorily regarding the quality of the top piling that is achieved. However, on account of their design, the fact is established that they cannot be operated at high operating speeds likely to correspond to the steadily increasing production speeds of the machines operating upstream of the batch stackers. Moreover, such devices involve the necessity of using a large number of drive systems for the various appliances which they include.